Mold for fiber sheets



April 26, 1932.

F. S. FARLEY ET AL MOLD FOR FIBER SHEETS Filed Nov/19, 1930 hud u urL lll I N VEN TOR:

L Ml

I 'Fifa Patented lAvpr. 26, 1932 UNITED STATES PATENT OFFICE v v FRANCIS S. FARLEY AND HUGO FELIX WALTER, OF TRENTON, NEW JERSEY, ASSIGNORS TO DANIEL MANSON SUTHERLAND, JR., OF MORRISVILLE, PENNSYLVANIA.

MOLD Eon FIBER SHEETS Application led November 19, 1930. Serial No. 496,618.

This invention relates tomolds for liber sheets and the like, and aims at improving such molds (especially as against the tendency of fiber sheets formed in them to stick to the molds), at lowering the cost of operation, and at improving the'product. How these and other advantages can berealized through the invention will appear from the 'I description hereinater of a selected and pre` ferred embodiment. A

In the drawings, Fig. I shows a vertical section through one form of mold conveniently embodying the invention.

Fig. II is a bottom plan view of the mold top.

Fig. III is a fragmentary sectional view, taken through the mold top as indicated by the line and arrows III- III in Fig. II; and,

Fig. IV is a similar view, taken as indi.

cated by the line and arrows IV-IV in Fig. II. p

In practice, raw fiber sheets for the manufacture of fiber board and the like are formed from aqueous pulp by draining or squeezing away the water, leaving the fibers interlaced in a porous, moist, frail aggregate that can afterwardbe consolidated or compacted into a board, usually by heat and pressure.

, One way of forming such a raw fiber sheet is by means of a mold of the general type illustrated in Fig. I, having a shallow, flat cavity into which the pulp is run fromhoppers 9, 9 opening into its opposite edges, and whence the Water is drained away when its opposite (top and bottom) wallsv10 and 11 are brought together. As here shown, the flat mold cavity is horizontal, and its top 10 is vertically movable relative to itsl bottom 11, which has a multitude of fine ducts 12, for draining olf the water, with a perforated or oraminous screen 13' over them. The edge walls or deckle 1,4, including the hoppers 9, 9, are also vertically movable,

9, 9 is run into the mold (which is suitably vented of air), filling the mold completely. The mold top 10 is then allowed or caused to4 descend, and the water of the pulp is thereby squeezed, strained, and drained oit through screen 13 and ducts 12, leaving the fibers behind interlaced and matted together in the form of a moist, raw sheet. )Vhen the top 10 has descended as far as its weight (or desirable additi-onal pressure) will carry it, the deckle 14 is raised Hush with the bottom surface'ot the mold top 10, or slightly higher, 'and the top 10 and deckle 14 are then further raised together, so that the formed fiber sheet may be carried away by the conveyor 15. Thereafter, the top 10 and deckle 14 are lowered again totheir positions of Fig. I, and the cycle ot' operations is repeated.

Now in practice, the raw fiber sheet formed in the mold tends to stick to the usual plain, flat lower surface of the metal plate forming the mold top 10 when the latter is raised, only breaking away and falling back on the conveyor wires 15 after hanging awhile,-or

even requiring to be manually loosened or started. This not only occasions delay, but also sometimes results in breken or damaged sheets.

In accordance with the present invention, such difficulties are obviated by a different sort of top mold lower surface: i. e., one of porous `,or elastic character, and preferably both. Elastic vulcanized rubber is a suitable elastic material, and can be had in sheets of sponge rubber that is quite porous,such as are used to make backing pads Jfor rubber stamps.

Fig. I shows the mold top 10 provided with a bottom facing pad 16 of sponge rubber, secured in any suitable way, as by cementn ing it to a metal backing plate 17 forming part of the mold top, and detachably secured by screws 18. Preferably, the backing plate 17 has its margins and corners augmented on a concave bevel, so as to produce a corresponding downward projection of the margins and corners of the pad 16, as shown in Figs. I, III and IV. For this purpose, strips 19 and corner-pieces 20 of wedge-shaped cross-section are shown attached to the lower face of the plate 17 at its margins,-which is a. less costly construction than to make the plate 17 itself with edges similarly augmented. These pieces 19, 2O may be of hard vul canized rubber cemented to the plate 17. Any suitable cement or adhesive may be used for attaching the pieces 19, 2O and the pad 16: e. g., ordinary shellac dissolved in alcohol. For this purpose, a rather thick shellac may be applied to both plate 17 and pad 16 (3 coats on theplate, and 1 or 2 on the pad), and the pad then applied to the platewhile the last coats of shellac are still fresh and wet. The shellac may then be allowed to set under the weight of the plate 17 resting on the pad 16: i. e., a pressure of about 10 lbs. per-square inch.

The facing pad 16 need not necessarily be in a single piece, but may, on the contrary, consist of a number of rectangular pieces 21 trimmed down from standard commercial t() in. X 10 in. sheets 1 in. thick, and arranged edge to edge (Figs. I and II). Preferably, the edges of these smaller sheets 2l are vulcanized together or cement-ed together with ordinary rubber cement, so as to form one large sheet 16 of the size required for a commercial wet machine, before being applied to the backing plate 17. As shown in Figs. I, III, and IV, the thus built-up rubber pad 16 is covered -or faced with a single sheet of textile fabric 22, preferably a wool felt about 15 in. or more thick. This covering 22 may be cemented to the pad 16 with ordinary rubber cement.

Fiber sheets made in a wet machine with a mold top 1() surfaced as above described do not stick to the mold top, but come away from itspontaneously as it rises, without really lifting from the conveyor wires 15. This is equally true without the felt covering 22,- whicli, indeed, need only be used to prevent the joints between theindividual rubber sheets 21 from marking the fiber sheets formed inv the mold. The felt 22 and its attachment by rubber `cement to the rubber pad 16 does not materially clog or occlude the pores of the sponge rubber, nor impair its 1absorptive power.

In operation, the 1 in. pad 16 compresses (as shown in heavy dotted lines in Figs. III and IV) to a thickness yof about 5/3 in. when the pulp is squeezed in the mold, so that its pores are flattened shut and remain uncharged with hvater, which drains away through the screen 13 just as fully as if the pad 16 did not exist. IVhen the pressure of the mold top 10 is released, however, the pad 16 eX- pands and its pores absorb the water from the top of the formed fiber sheet. The edges of the pad 16 pack against the deckle walls and prevent water from the pulp from Working up around the edges of the top 10; and if any Water does work up in this manner, the edges of the pad absorb it when the deckle 14 is raised, and keep it from dripping on the liber sheet and wetting its edges. The pad 16 also acts as a cushion to protect the conveyor wires lrif the top 10 should inadvertently be lowered on the bottom 11 with the mold empty. While the edges and corners of the pad 16 compress and deflect more than its central portion under the same loading, as indicated by the heavy dotted lines in Figs. III and IV, this is compensated for by the wedges 19, 20, so that the resultant liber sheet is of uniform thickness right out to its very edges.

Having thus described our invention, we claim:

l 1. In a mold of the character described, for forming sheets from fiber pulp by squeezing out the water, a mold top faced with elastic sponge, whereby sticking of the formed fiber sheet to the top is prevented.

2. In a mold of the character described, for forming sheets from fiber pulp by squeezing out the water, a mold top comprising a metal plate and a facing pad of sponge rubber cemented thereto, whereby sticking of the formed fiber sheet is prevented.

3. In a mold of the character described, for forming sheets from fiber pulp by squeezing out the water, la mold top having a pad of elastic sponge sheets secured thereto, edge to edge, and a sheet of porous fabric secured over said facing, so as to prevent its joints from marking the fiber sheets formed in the mold.

4. In a mold of the character described, for forming sheets from fiber pulp by squeezing out the Water, a mold top having a fiat bottom surface with swelling edges and corners, and a facing pad of elastic sponge, of substantially uniform thickness over said top, including its edges and corners, whereby a fiber sheet of uniform thickness is produced in the mold, and sticking of the sheet to the Amold top is prevented when the mold is opened.

5. In a mold of the character described, for forming sheets from fiber pulp by squeezing out the water, a mold top comprising a fiat metal plate, Wedges secured thereto along its edges, a facing pad of sponge rubber cemented to said plate and wedges, and a -sheet of porous fabric cemented over saidpad.

In testimony whereof, we have hereunto signed our names at Trenton, New Jersey, the 10th day of November, 1930.

/ FRANCIS S. FARLEY.

HUGO FELIX WALTER. 

